The project is intended to monitor changes in dental plaque organisms, specifically Strep. mutans, during fluoride preventive procedures provided to a school population over a two year period. Serotypes of Strep. mutans are characterized and enumerated in plaque from individuals using fluoride rinses either daily or weekly, as well as from individuals using a placebo solution. Fluorescent Antibody (FA) reagents specific for the serotypes of Strep. mutans are employed to detect changes in the students' plaque samples. Alterations in the plaque composition during the study period will be related to the changes in the caries incidence.